In a production process of an ultra-highly integrated semiconductor device such as DRAM or MPU, forming a thin film of Si3N4, polysilicon or the like as a gate insulting film or a capacitor on a surface of a semiconductor wafer is one of important processes. Formation of such a coating film on the surface of a semiconductor wafer is generally conducted using a low pressure CVD device. And various kinds of jigs such as a wafer boat using SiC or the like as a jig base are used in such a low pressure CVD device.
For example, as a jig using SiC as a jig base, there may be mainly used a product in which a porous SiC sintered body obtained by adding a binder to an SiC powder as a raw material, followed by molding, calcining and degreasing is impregnated with molten metal silicon (Si) to completely fill its pores with Si, thereby achieving gas-impermeability. Then, a surface of such a jig is coated with a protective film such as an SiC coating film, thereby suppressing diffusion of impurities to the outside from the inside of the jig.
In a semiconductor production process, a semiconductor wafer is placed on such a jig, and a thin film of Si3N4, polysilicon or the like (hereinafter referred to as a “deposit film”) is formed on the wafer surface by a CVD method. In such a case, the deposit film is unavoidably formed on the surface of the jig.
A jig having the surface coated with an SiC coating film or the like has a problem that a deposit film peels from the surface of the jig at a relatively early stage, and particles and the like are generated. Therefore, the jig surface is required to be frequently cleaned with hydrofluoric acid, fluoronitric acid or the like to remove the deposit film adhered to the surface. To enhance production efficiency of a semiconductor and to improve product precision, those deposit films are required to make difficult to peel from the jig surface. Therefore, attempt to enhance the adhesive force of the deposit film by roughening the jig surface is conventionally conducted.
For example, Patent Document 1 mentioned below discloses an SiC jig characterized in that in an Si-impregnated SiC jig on which an SiC coating film is coated by CVD used in a low pressure CVD device in a semiconductor production process, a thickness of the SiC coating film coated is from 20 to 150 μm, and an average surface roughness Ra of the SiC coating film is from 1.5 to 5.0 μm.
Patent Document 2 mentioned below discloses a member for processing a semiconductor characterized in that, in a member for processing a semiconductor which is consisting of a silicon carbide film or in which a silicon carbide film is formed on a surface of a base substance of the member for processing a semiconductor used in a semiconductor production process, a surface roughness of the surface of the silicon carbide film is 150/cm or higher in peak count (Pc) when a dead zone width and measurement length of using a surface roughness measuring device is set 0.3 μm and 4 mm, respectively, and the surface of the silicon carbide film has an amount of fluorine atom of 0.3 atomic percentage or less, an amount of organic nitrogen of 0.7 atomic percentage or less, an amount of a hydrocarbon component of 29 atomic percentage or less, and an amount of organic CO of 4 atomic percentage or less in X-ray photoelectron spectrometry.